Derivation calculation

[Martin88]

Hi Forum,

I would like to stream a  waveformdata to a tdms file  until the signal (see attachment)  is not more rising, is there a function in labview that could give me the derivation of the signal and stops as soon it reaches that level?

Thanks in advance

Martin

[ogk.nz]

Assuming that you do not know the value at which the measurements are going to level out, would it not just be easier to take the last 5 measurements from the array and examine the difference between each number and the one preceding it? You could then stop the program if the maximum difference is less then some threshold.

[Martin88]

Yes the problem is that he threshold it is variable so i cant set it on a known value. You mean i could calculate the difference between each sample and set a threshold to stop it? 

[ogk.nz]

Thats the general idea. See the attached snippet for an idea of what to do.

[Martin88]

Hi thanks for your answer,  as i understand I still ihave to set a threshold on this example the problem is the threshold would be always different.  

[jcarmody]

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@Martin88 wrote:

Hi thanks for your answer,  as i understand I still ihave to set a threshold on this example the problem is the threshold would be always different.  

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I think you may be misunderstanding the suggestion.  The "threshold" isn't the value that the waveform stops rising, it's the difference in successive points that lets you decide that it's no longer rising.  If you used one of the derivative VIs, you'd still need to decide how close to zero the slope needs to be to decide that it's not rising any more.  That'd be the same "threshold" that you'd use here.

It's certanily possible that I'm misunderstandind the suggesting.  In which case, ignore me.